Evaluation of Boneloc. Chemical and mechanical properties, and a randomized clinical study of 30 total hip arthroplasties.

We evaluated the mechanical, chemical and clinical properties of Boneloc cement using radiostereometry and a series of laboratory tests. Compared to a standard cement (Palacos) the new cement displayed reduced tensile strength, elastic modulus, curing and glass transition temperatures. The amount of MMA extracted during 3 weeks in methanol was smaller for the Boneloc, but the total amount of released monomers was larger. The adhesion to stainless steel and bone did not differ. Radiostereometric analysis during the first postoperative year in 30 patients randomized to fixation of hip prostheses using either of the 2 cements displayed increased proximal migration of the cup and increased stem subsidence when Boneloc had been used. Part of the stem subsidence occurred inside the cement mantle. On the basis of these findings, we conclude that the inferior fixation in the Boneloc group is mainly caused by its mechanical properties. Other mechanisms, such as increased release of monomers, may also be important.